In display devices such as liquid crystal display devices, a switching element is provided for each pixel. When, for example, a backlight emits light to the channel area of a semiconductor layer in the switching element, leak current may be generated. Thus, a technology for using a metal layer to shield the channel area of the semiconductor layer from light has been suggested.
The metal layer is normally floating. Thus, the metal lines may be coupled to signal lines which supply video signals and pixel electrodes. In this way, the potential of the pixel electrodes may be changed by the effect of the potential of the signal lines. This effect is notably seen in pixels with high fineness. The change in the potential of pixel electrodes is visually recognized as a flicker, and leads to reduced display quality. When the pixels are driven at a low frequency, a flicker is easily recognized.